Looks like something I did way back in elementary school (as the first person said, chromatography). Involves putting the ink on paper of some sort and using a solvent, though if I remember right we just used water in my elementary class. Eventually the ink bleeds and creates a bunch of colors on the paper.
I used to draw with a ballpoint when I was bored in school. Nothing as good as this, of course. But I learned that the ball point is more versatile than most people realise, and changing the pressure can yield a variety of shades.